Method for repairing a gas turbine component

Abstract

A method for repairing an ex-service gas turbine component ( 10 ) includes the steps of: removing a damaged section ( 13 ) from the gas turbine component ( 10 ), manufacturing a 3-D article, which fits in the gas turbine component ( 10 ) to replace the removed damaged section ( 13 ), and joining the gas turbine component ( 10 ) and the 3-D article inserted therein. Reduced cost, improved flexibility and productivity, and simplified handling are achieved by removing the damaged section ( 13 ) in the form of a cut-out section along a split line ( 14 ) as one single cut-out piece ( 15 ), measuring the cut-out piece ( 15 ) to obtain the actual non-parametric geometry data set of the cut-out piece ( 15 ), and manufacturing the 3-D article based on the geometry data set of the cut-out piece ( 15 ).

1 . A method for repairing an ex-service gas turbine component comprising:
 removing a damaged section from said gas turbine component;   manufacturing a 3-D article which fits in said gas turbine component to replace the removed damaged section; and   joining said gas turbine component and said 3-D article inserted therein;   wherein removing the damaged section comprises removing in the form of a cut-out section along a split line as one single cut-out piece;   measuring the cut-out piece to obtain the actual non-parametric geometry data set of the cut-out piece; and   wherein manufacturing said 3-D article comprises manufacturing based on said geometry data set of the cut-out piece.   
     
     
         2 . A method according to  claim 1 , further comprising:
 creating a virtual 3-D article in the form of a CAD model from said measured geometry data.   
     
     
         3 . A method according to  claim 2 , wherein creating a virtual 3-D article comprises virtually rebuilding damaged or missing areas of the cut-out piece to create, modify, extend, or combinations thereof, said CAD model. 
     
     
         4 . A method according to  claim 2 , wherein the CAD model includes information about the inner surface, potential distortions, local wall thickness modifications, and positions of cooling air holes of the ex-service gas turbine component. 
     
     
         5 . A method according to  claim 1 , further comprising:
 adding an additional material surcharge around at least part of the split line to the geometry data set of the cut-out piece to allow for
 a compensation of the material loss due to cutting, 
 the preparation of a split line surface, 
 a final or individual adaptation of a standard 3-D article geometry to the individual ex-service gas turbine component to be repaired, 
 or combinations thereof. 
   
     
     
         6 . A method according to  claim 1 , wherein manufacturing the 3-D article comprises manufacturing by an additive manufacturing technology. 
     
     
         7 . A method according to  claim 6 , wherein the additive manufacturing technology is selected from the group consisting of selective laser melting (SLM), selective laser sintering (SLS), and electron beam melting (EBM). 
     
     
         8 . A method according to  claim 1 , wherein manufacturing the 3-D article comprises manufacturing by investment casting or milling. 
     
     
         9 . A method according to  claim 1 , further comprising, before said joining the manufactured 3-D article into the ex-service gas turbine component:
 recontouring the manufactured 3-D article into a recontoured 3-D article to reach optimum conditions of the split line surface, gap width for the final joining process, or both.   
     
     
         10 . A method according to  claim 9 , wherein recontouring comprises removing a fixed thickness of material. 
     
     
         11 . A method according to  claim 9 , wherein recontouring comprises individual adaptive machining. 
     
     
         12 . A method according to  claim 11 , wherein said adaptive machining is based on the individually scanned ex-service gas turbine component, which is compared with the 3-D article geometry. 
     
     
         13 . A method according to  claim 11 , wherein said adaptive machining uses a geometry data set based on the evaluation of a limited number of scanned gas turbine components of the same kind. 
     
     
         14 . A method according to  claim 9 , wherein recontouring comprises a subtractive machining process. 
     
     
         15 . A method according to  claim 14 , wherein said subtractive machining process is selected from the group consisting of milling, grinding, and electro chemical machining (ECM). 
     
     
         16 . A method according to  claim 9 , wherein recontouring further comprises heat treatment, chemical cleaning of the surfaces, or both, of the 3-D article to make the 3-D article ready for insertion. 
     
     
         17 . A method according to  claim 1 , wherein said joining of said gas turbine component and said 3-D article comprises brazing, welding, or a combination thereof.